Rotary pump



Jan. 7, 1930. w, E HQKE 1,742,597

ROTARY PUIP Y Fld lay 20;. 192'7 .l 5 ShestsFSheet 1 INVENTOR ATTORNEYSJan. 7, 1930. w. EjHoKE 1,742,597

ROTARY PUIP Filed lay 20. 1927 3.Sheets-Sheet 2 INVENTOR ATTORNEYS Jan.7, 1,930. w, E, Hem.; 15742,',597

f ROTARY PUIP Filed un; 2o. 192'?l s sheets-sheet s I Q/ 7*, i 5. E ImvlToR .lzzV "Bla/g ATTORNEYS Patented Jan. '7, 1930 UNITED s're'riasPATE-NT OFFICE WILLIAM. EBEN ,HOKE F BALTIMORE, MARYLAND, ASSIGNOR TOJOSEPH MERCA- DANTE, OF NEW YORK, N. Y.

vno'ran'z PUMP Application mea my 2o,

This invention relates to rotary iumps of the General type disclosed inthe roh Patent o. 1,495,411, issued May 27, 1924, and it includes notonly improvements in pumps 0f this character, but also improvements ingears suitable for use in rotary pumps and improvements in'methods ofmaking such gears.v

Rotary pumps of the character described in the said Patent No. 1,495,411comprise a pump chamber casing enclosing intermeshing lgears- In theoperation of the pump, the

fluid being pumped or compressed enters the spaces between the gearteethas they disengage and the Huid is discharged from these spaces into thehigh pressure side of the system. As the gear teeth come into mesh. allof the fluid occupying the tooth spaces with thcexception of theclearance spaces is expelled, and where a gas is being pumped, asuitable cooling fluid such as oil is relied upon to prevent communi-.cation between the high and low pressure sides of the pump systemthrough the clearance spaces. A' considerable quantity of sealing fluidis ordinarily employed for this purpose, and even at best there is someleakage of the pumped fiuid from the'high pressure side of the system tothe low pressure side. The use of a considerable quantity of sealingfiuid presents a number of difficulties which have heretofore beenconsidered unavoidable. The normal action of the pump causes the sealingfluid to foam, and various attempts have been made to preserve thequality of the scaling fluid, as b v cooling the same. Furthermore, itis ver v difiicult. if not impossible, to prevent some ot' the scalingfiuid from hecoming so intimately associated with the pumped fluid as torender the separation of these n'iaterials impossible except by the useof special apparatus designed for this purpose. p

Une of the objects of my invention is to provide a rotary pump in whichit is unnecessary to use the usual quantity of sealing fluid, it beingTnecessary'to merely employv enough oil to lubricate the parts. A furtherobject of this invention is to provide a rotary pump of higherefficiency than those heretofore used, arid this b v virtue of the factthat gears of an improved character are employed, the gears 1927. SerialNo. 192,550. v

vide a. gear pump having an inlet port extend- A 'ing'substantially tothe center line, passing through the axes of the gears, whereby theenlarging tooth spaces remain in communication with the fluid supplyuntil the spaces are entirely filled.

A further objectis to provide a rotary pump having spirally cut gearsand a discharge' or relief port extending substantially to the verticalcenter line passing through the axes of the gears, to thereby preventtrapping of liquid between intermeshing teeth as they come together.This prevents the hammering action ordinarily encountered With pumps ofthis type,a11d renders the operation of thepump noiseless. Still anotherobject of my invention is to provide gears for rotary pumps havingteeth, the profiles and root outlines of which comprise a continu- -ousdevelopment or generation of the gear tooth curve, and as stated above,my invention includes an improved method of making the gears justdescribed.

My improved method includes the' use of a reversibly symmetricalrack-like cutter for forming the improved gears, the gears being formedin such a manner that no appreciable clearance space is provided. Itwill be understood, however, that gears of the improved type can be madeby the use of means other than this particular form of gear cutter.

The various objects and advantages of my invention will be more apparentupon considering the following detailed description, which is to betaken in conjunction with the accompanying drawings, in which I haveillustrated certain embodiments of my invention. In the accompanyingdrawings,

Fig. 1 is an enlarged fragmentary View of two intermeshing gears made inaccordance with my invention;

Fig. 2 is an enlarged fragmentary view of one of the improved gears anda cutter suitable for making the gear;

Figs. 3 and 4 are enlarged fragmentary views of other forms of gearcutters;

Fig. 5 is a vertical section -view taken on line 5-5 of Fig. 7;

Fig. 6 is a transverse section view taken on line 6-6 of Fig. 5, showingdetails of construction;

Fig. 7 is a transverse section view takenon lineT--T of Fig. 5, showingdetails of construction y Fig. 8 is an end elevation of the pump shownin Fig. 5;

Fig. 9 is a transverse section view taken on line 9--9 of Fig. 5,showingdetails of construction;

Fig. 10 is a transverse section view taken on line 10-10 of Fig. 5,showing the construction of the pump casing;

Fig. 11 is a transverse section view taken on line 11-11 of Fig. 5,showing details of construction; and

Figs. 12 and 13 are perspective views of a spirally cut gear made inaccordance with my invention.

The accompanying illustrations-of certain embodiments of my inventionshow gears having teeth the profiles and root outlines of which comprisethe continuous development of a gear toothcurve, one of thecharacteristics of the gears being that the crowns of the teeth of onegear are adapted to bottom or make contact with the corresponding rootportions of the gear inter-meshing therewith. In other words, the gearteeth are so shaped that all portions thereof, from the lowest pointsofthe roots to the highest points of the crowns. cooperate in gearaction during the rotation of the inter-meshing gears. In ordinarygears, the root circle, which bounds the bottoms of the tooth roots, islower than the working depth circle or the circle bounding the extent towhich a tooth crown on a coopera't-ing gear enters a tooth root. Thusthe portions of ordinary gear teeth below the working depth circles, aswell as the portions of the crowns tangent to the adendum circle, do notcooperate in gear action because they do not follow developments of anygear-.tooth curve. In the gears of the present invention, the rootcircles and working depth circles are coincident, the tooth profiles androot outlines being continuous developments of a gear tooth curvethroughout. Thus gear action takes place over the entire surface of eachgear tooth during the rotation of the cooperating gears.

The gears ofthe present invention are preterably formed to engagewithout back-lash, that is, the thickness of each tooth is equal to thetooth space into which it meshes when measured on the pitch circle.

In Fig. 1for example, I have illustrated a gear A, meshing with the gearB. and the tooth profiles 1 and the root outlines 2 of gear A arecontinuous developments or generations of the gear tooth curve. The sameis true of the tooth profiles 3 and the root outbe made by utilizing areversibly symmetrical rack-like cutter having sharp pointed teeth.

The teeth and spaces of the rack are equal and symmetrical, or in otherwords, each tooth and the adjacent space are bounded by similar andequal lines of alternating reversion. It may be stated that if two racksof this character be fitted together, the teeth of one will exactly titand fill the spaces of the other. One is the complement of the other,and the teeth and spaces will be exactly equal as measured on the pitchline. Gears cut by means of such a rack cutter are conjugate to the rackand to each other, and inasmuch as no clearance is provided, each toothis adapted to make contact at a plurality of points Ywith theintermeshing gear.

For example, one ofthe teeth of gear B in Fig. 1 is shown making contactwith gear A at 5,- 7 and 8. The gears are shown in the preferredadjusted position in which there is no back-lash.

The teeth of the rack cutter may be of any desirable form, the importantconsideration being that the cutter should be reversibl symmetrical. InFigs. 2, 3 and 4, I have i lustrated forms of teeth different from thesharp pointed teeth just described. The teeth shown in Fig. 2 areprovided with straight sides 9, with a rounded crown 10, and acorrespondingly rounded root portion 11. The tooth shown in Fig. 3 isprovided with straight sides 9', with a. flat crown 10', and a 'lat rootportion 11. The tooth shown in Fig. 4 is provided with curved sides 9,with a rounded crown 10 and correspondingly rounded root portions 11".The involute system of tooth curvescan be employed using any portion ofthe curve with the result that the gears have all of the advantagesincident to gears having teeth of the involute type. Other standardsystems may likewise'be employed.

In Figs. 5 to 11 inclusive, I have illustrated one embodiment of myinvention as applied to rotary pumps. In these figures, 12 represents aportion ot' a pump casing of any suitable form, it being understood thatthe pump gears 13 and 14 are enclosed within the casing, a part of whichis shown at 12. The gear 14 is keyed or otherwise fixed to a shaft l5journaled in the casing 12 and in hearing plates 16 and 17. The shaft 15projects through the casing wall and is driven by any suitable means(not shown). Suitable packving 18 is provided around the shaft 15, 1naccordance with usual practice. The gear 14 meshes with gear 13 and iscarried by a shaft 19 journaled in the bearing plates 16 and 17.

n supply the fluid directly to .the tooth spaces of the gears 13 and 14.As the gear teeth disengage, the fluid is drawn into the enlarging toothspaces until they are substantially filled with the fluid. Thereafter,the fluid is trapped in these spaces by the curved surfaces 2l and 22 ofthe segmental housing 20. As the advancing gear teeth leave the extremeportions of the segmental housing, the fluid is discharged into theinterior of the pump casing.

I prefer to form the passage 24.in such manner that the delivery endthereof extends substantially to the center line of the pump passnthrough the axes of the gears 13 and 14,A as est shown in Fig. 6. Viththis arrangement, it is possible to fill the tooth spaces completelybefore communication therewith is cut olf by the curved portions 21 and22 of the segmental housing 20. The gears 13 and 14 are spirally cut andof the type above described and illustrated in Figs. 1 to 4 inclusive,and 12 and 13. The pitch of the spirally cut teeth is preferably suchthat one pair of cooperating teeth does not become entirely disengageduntil the next pair begins to come into engagement. Accordingly, thereis never a through passage along the gear tooth spaces from the interiorof' the pump casing to the fluid supply passage 24.

In Figs. 12 and 13, I have attempted to illustrate some of thecharacteristics of my improved gears which render them particularlyvaluable as the movin elements of a rotary pump. In these two hgures,which are perspective views of a spirally cut gear made in accordancewith my invention, the dotted line represents the line of Contactbetween two intermeshing gears of this form. Fig. 13 shows the gear ofFig. 12 in a slightly different position. As shown by the dotted line,the line of contact or line of seal between two intermeshing gears ofthis form is continuous, and in the particular instance illustrated,extends across the crowns of two adjacent teeth. lVith gears of ordinaryconstruction, the line of seal or line of contact is not continuous; itis interrupted at the crowns of the interengaging teeth due to theclearance space.

Vith the particular gear shown in Figs. 12 and 13, the line of contactor line of seal, although continuous, is made up of a number of parts,seven parts being shown in Fig.

13 as a., b, c, (l, e, f and g. Upon referring to Fig. 12, it Will benoted that the portion g of the line of seal or line of Contact is inalignment with the portion c, these two portions being on correspondingfaces of adjacent teeth. The particular gear illustrated in Figs. 12an-d 13 is of the involute form,

'the tooth profiles and root outlines being a continuous development orgeneration of the gear tooth curve.

Referring again to Figs. 5 to 11 inclusive,

it will be noted that the inner bearing plate 16 is provided on theinner face thereof with a depression 25 communicating With a pipe 26bymeans of a channel or passage 27. Lubricating or sealing fluid can besupplied to the depression 25 through the pipe 26 and where the pump isused for the purpose 0f compressing a gasified refrigerating medium suchas sulfur dioxide, the usual sealin fluid such as oil can be supplied tothe 4pipe 26 from the interior of the pump casing. T he sealing Huid orlubricating fluidv may gain access to the gears 13 and 14 through smallpassages'28 and 29, best shown in Figs. 7, 9 and 10. Thesepassages-communicate with those portions of the gears 7 in contact withthe segmental housing 20, and the sealing fluid may serve the purpose ofcompressing the gaseous fluid trapped in the tooth spaces.

lVhere my invention is employed, it is not necessaryto use as muchsealing fluid as is ordinarily employed; it is quite sufficient tomerely employ enough of the fluid to lubricate the gears. This desirableresult is made possible because of the form of the gear teeth which, aspointed out above, are capable of 'forming a continuous line of sealfrom one end to the other.

In order that all of the liquid in the tooth spaces may bereadilyexpelled as the gear teeth come together, I provide an exhaust port 30in the outer bearing plate 17. This port may extend substantially to thevertical center line passing through the axes of the gears, thuspermitting all of the liquid in the gear tooth spaces to be discharged,thus eliminating the trapping of any of this liquid, as is ordinarilythe case in rotary pumps. It is ordinarily impossible to locate thedischarge port very close to the vert-ical center line of the pumpbecause in the ordinary pump this would result in the escape of thepumped .fluid from the high pressure side of the system to the loWpressure side through the gear tooth spaces. This discharge iseliminated by the use of gears made in accordance with myrinvention'.

It. is to be understood that my invention is not limited to theparticular embodiments illustrated and described, but include suchlnodifications thereof as fall within the scope of the appended claims.For example, my improved gears can be formed by using cutters other thanthose herein described in detail; my invention can be applied to .gearsof any type, and the details of the pump mechanism can be modified andin some instances even eliminated Withoutsacrificing all of the 5advantages of my invention.

I claim: v

1. In apump, the combination with the pump chamber casing, ofintermeshing sp1- rally cut gears, means for introducing the lo pumpedfluid into spaces between intermeshlng teeth at one end of the gears,means for introducing a sealing liquid into said spaces, and meanspermitting escape of said liquid from between the teeth at the pointWhere the opposite end of the teeth are completely or fullyintermeshed;`

2. In a pump,'the combination with the pump chamber casing, ofintermeshing spirally cut gears, means for introducing the pumped fluidintospaces between intermeshing teeth at one end ofthe gears, means forintroducing a sealing liquid into said spaces, and means at the oppositeends of vthe teeth for receiving sealing liquid forced from betweenintermeshinf teeth at said opposite ends, said means being located at a,point where the teeth at said opposite end are fully intermeshed.

3. In a pump, the combination with the pump chamber casing, ofintermeshing spirally cut gears, means for introducing the pumped fluidinto spaces between intermeshing teeth at one end of the gears, meansfor introducing a sealing liquid into said spaces,

and end plates enclosmg the ends of the gears, the plate at the endopposite the point of admission of pumped fluid having a relief recesstherein located at the point at which the adjacent ends of the teeth arefully in- 4 termeshed.

4. In a pump, the combination with the pump chamber casing, ofintermeshing spirally cut gears, means for introducing the pumped Huidinto spaces between intermeshing teeth at one end of the gears, meansfor` introducing a sealin liquid into said spaces, and end platesenclosing the ends of the gears, the plate at the end of the gearsremote from the point of admission of the pumped fluid having a ducttherein extending from its eX- terior face to a point on its interiorface in registry with the point at which the teeth fully intermesh atthat end of the gears.

In testimony whereof I aiix my slgnature.

WILLIAM EBEN HOKE.

